docs: def win_find_exe(filename, installsubdir=None, env="ProgramFiles"):
      """Find executable in current dir, system path or given ProgramFiles subdir"""
      for fn in [filename, filename+".exe"]:
          try:
              if installsubdir is None:
                  path = _where(fn)
              else:
                  path = _where(fn, dirs=[os.path.join(os.environ[env], installsubdir)])
          except IOError:
              path = filename
          else:
              break        
      return path